Direct-acting sound-reproducing device



June 18, 1929. A, MCL, NicoL N 1,717,463

DIRECT ACTING SOUND REPRODUCING DEVICE v Filed April 2, 1927 INVENTOR ALEXANDER Mc LEAN NlCflL SDN TTORNEY Patented June 18, 1929.

UNITED STATES ALEXANDER MGLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR TOWIRED RADIO,

INQ, OF NEW YORK, N. Y., A. CORPORATION OF DELAW E.

DIRECT-ACTING SOUND-REPRODUOING DEVICE.

Application filed April 2,

This invention relates to sound reproducing apparatus and more particularly to apparatus arranged to be operated by electrical oscillations, corresponding to the sound to be I reproduced, and operating ,to convert such oscillations into sounds corresponding thereto.

It is an object of this invention to provide improved apparatus utilizing the phenomena to of resonance or partial resonance, to convert electrical oscillations into sound.

It is a further object of this invention, to provide improved apparatus of the class described, utilizing a multiplicity of direct acting sound radiating elements such as sounding boards, "having difierent natural frequencies, for converting electrical oscillations into sound.

It is a further object of this invention to provide improved apparatus for converting electrical oscillations into sound corresponding as closely as possible to the original sound which it is desired to reproduce. Still other objects of my invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its underlying principles and as to its ractioal application will best be understood y refer ence .to the s ecification and accompanying drawing, in w ich the single figure is a front elevation partly in section of apparatus ac- 5 cording to my invention.

In accordance with my invention, I provide a plurality of direct acting sound radiating surfaces such as sounding boards. The sounding boards are so constructed and arranged that each has a different natural frequency: to this end, they may be of different sines, shapes, materials, or may difier in physical characteristics in any way desired to rovide the desired operating characteristics.

The said sounding boards are chosen so that their natural frequencies are distributed over the range to be covered, are secured together in spaced relation by means of one or more mechanical connections which may act simultaneously asa medium for transferring the acoustic vibrations to each of the sounding boards.

A suitable driving means adapted to con- 1927. Serial No. 180,419.

vert electrical oscillations into corresponding acoustic vlbratlons is associated with the 5 chain of sounding boards already described,

tions into acoustic vibrations such for ex- 0 ample as an electro-magnetic unit, but for certain purposes I prefer to use a piezoelectric crystal device such for example as a crystal of Rochelle salt exhibiting the well known hour-glass configuration. crystal device or other suitable driving means is associated mechanically with at least one of the sounding boards or with the vibration transmitting connection therebetween or with both, and is provided witha pair of electrodes between which may be impressed the electrical oscillations corresponding to the sounds which it is desired to reproduce.

My invention is shown in the accompanying drawing in side elevation, illustrating the multiplicity of sounding boards and the connection thereof with the source of sound vibrations.

Referring now more particularly to the draw1ng,'1, 2, 3 and 4 designate respectively a plurality of sounding boards of different size and shape, and if desired of different material such as different kinds of wood, or if desired material other than wood, such for example as hard rubber, bakelite, or even metal if desired. The driving plate 5 preferably of elastic metal such as steel or duralumin is provided adjacent the sounding board 4 and the assemblage is maintained in roper spaced relation by means of suitable olts 6 9 and 7 passing through each of the sounding boards and through the plate 5.

Suitable spacing members 8 may be inter posed upon the bolt 6, and similar spacing members 9 upon the bolt 7 for the purpose of maintaining the various sounding boards at the desired distance from each other. Suitable nuts 11 mounted upon the bolt 7 and similar nuts 12 mounted upon the bolt 6 are provided for maintaining the various ele-" ments in proper position and suitable washers 13 of leather, felt, or other absorbent material are interposed between the nuts and the plate 5 and any other metal to metal joints where necessary to prevent rattling.

A suitable piezo-electric crystal 10 such for Said on example a crystal of Rochelle salt exhibiting the well known hour-glass configuration is mounted upon the plate in any suitable manner as for example by cementing thereto with Rochelle salt melt comprising Rochelle salt'from which the desired amount of water has been removed by heating it at a temperature above its melting point. For the purpose of maintaining the crystal in position and for applying acompressive stress to it, there may be provided a U shaped clamp havin ends 16 and 17 ,adaptedto be mounted upon olts 6 and? respectively and to be secured in position thereon by means of suitable nuts 18 and 19. The crystal 10 is protected by a suitable casing 22 having an opening therein-to permit the cushion 2 3 to extend th'erethrough. The cushion 23 may be of suitable material such as rubber, cork,

leather or soft metal,-or the like, and is in turn operated by a spacing element 24. The casing 22 'is provided with an extension 25 of flexible material such as copper on the out- 'side of which is adapted to operate the clamping screw 26 having a head formed to engage the casing 25 and through it'the cushion 24.

The screw 26. may be provided with a slot in the outer end by means of which the same ma be positioned as desired, and a suitable loc nut 28' is also provided for the purpose of securing the parts in the, proper position.

A pair of electrodes are provided for operatin the crystal 10.

n. theform shown, the plate 5 may con stitute one of these electrodes and the other may be constitutedby an interior electrode 21 mounted within the ;crystal. The exact form ingg'gelasticity, etc., and the number and arrangement of sounding boards is so chosen as to give a substantially flat response characteristic over the range desired.

While I have shown and described certain preferred'embodiments of my invention, it will be apparent that modifications and changes may be made without departing from the. spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. .An acoustic device comprising a plu- "rality of sounding boards having different natural frequencies, I means for converting electrical oscillations into acoustic vibrations for drivingsaid sounding boards, and a pair of independent connections extending beextending normal to each of said sounding boards for transferrin sound vibrations from said means to ea'dli of said sounding boards.

3. An acoustic device comp risin a plurality of sounding boards having di erent natural frequencies, means for, converting electrical oscillations into acoustic vibrations for driving said sounding boards, a pair of rod members-extending normal to the plane of said sounding boards and securing said sounding boards in parallel spaced relation, while transferring sound vibrations from said means to said sounding boards.

4. An acoustic device comprising a plurality of sounding boards of different sizes and shapes having different natural frequencies, means for converting electrical oscillations into acoustic vibrations for driving said sounding boards, a pair of rod members extending normal to the plane of said sounding boards and securing said sounding boards in parallel spaced relation, while transferring sound vibrations. from said means to said sounding boards. 5. An acoustic device coniprisin a plurality ofsounding boards having di erent nat- '1 ural frequencies, a pair ofvibration-trans mitting connections between said sounding boards, and means for converting electrical oscillations into acoustic vibrations and for applying said vibrations to said connections. 10:; 6. An acoustic device comprisin a plurality of sounding boards having di erent natural frequencies disposed in spaced relation, a plurality of vibration-transmitting connections between said sounding boards, and means for converting electrical oscillations into acoustic vibrations and for applying said vibrations to said connections.

7. An acoustic device comprising a plurality of sounding boards of different sizes and shapes having different natural frequencies disposed in parallel spaced relation, 9. pair of vibration-transmitting connections between said sounding boards for maintainin said sounding boards in selected space relation, 1

and means for converting electrical oscillations into acoustic vibrations and for applying said-vibrations to said connections.

8. An acoustic device com rising a plurality of sounding boards of fi rous material of diiferent sizes and shapes having differ- "ent natural frequencies disposed in spaced relation, and a pair of vibration-transmitting connections between said sounding boards for maintaining said sounding boards in selected space relation, an elastic metallic mounting plate secured to said vibration-transmitting Connections, and means for converting electrical oscillations into acoustic vibrations mounted on said plate.

9. An acoustic device comprising a plurality of sounding boards of fibrous material of different sizes and shapes having different natural frequencies disposed in spaced relation, and a pair of vibration-transmitting connections between said sounding boards for maintaining said sounding boards in proper space relation, an elastic metallic mounting plate secured to said vibrationtransmitting connectlons, and means for converting electrical oscillations into acoustic ALEXANDER Hell-IAN NICOLSON. 

